1. Field of the Invention
This invention relates to a briquetting press and more particularly to an industrial-sized briquetting press. The press includes apparatus for improving contact between the peripheral surfaces of the briquette-forming rolls and for improving the accessibility of the components of the press for maintenance and repair.
2. Description of the Prior Art
A briquetting press produces briquettes by compressing particulate material between two cooperating rolls, the peripheral surfaces of which contain cavities into which the particulate material is compressed. In order to produce briquettes of uniform shape, the lines of tangency of the peripheral surfaces of the rotating rolls must be as close to parallel as possible at the point where the particulate material is compressed in the cavities. However, the insertion of the particulate material between the peripheral surfaces of the rolls causes the rolls to spread apart. Accordingly, to minimize the splitting, shearing or deforming of briquettes, there must be a means for permitting the rolls to separate while keeping the lines of tangency of the peripheral surfaces of the rolls substantially parallel at the point where the briquettes are formed. The radii of the rolls should be maintained substantially in the original plane, that is, the plane normal to the plane containing the axes of rotation of the rolls.
By way of explanation, consider two points, one on each of the peripheral surfaces of the rolls, which are in a plane defined by lines of radius of the rolls and which are opposite each other when the surfaces are together at the briquette-forming point. These two points are also on lines which are mutually tangent to the surfaces of the rotating rolls and perpendicular to the plane formed by the lines of radius of the rolls. Ideally, when the rolls spread apart due to insertion of particulate material, the two points should remain in their original plane and the separated lines of tangency passing through the two points should remain parallel.
Achievement of the ideal is not presently feasible for large briquetting machines. The alternative is a design which, during roll separation, reduces the deviation of the two points from their original plane to a minimum and keeps the projected angle between the lines of tangency as close to zero as possible.
The prior art devices attempted to solve the separation problem by permitting both rotating rolls to articulate about points on the longitudinal axis of the drive shafts of the rotating rolls. The farther the point was from the roll, the less arc the rolls traveled and thus the deviation of the points from their original plane and the angle between the lines of tangency on the surfaces was reduced. While this design reduced the deformation of briquettes, it proved to be inadequate as the diameter of the rotating rolls was increased.
Having the point of articulation on the longitudinal axis of the drive shaft of the rolls was not satisfactory for large, industrial-sized briquetting presses. Assume, for the sake of comparison, that the radius of articulation of the smaller briquette-forming rolls is equal to that necessary for the larger briquette-forming rolls. If, in both cases, when the rolls spread apart they travel through the same number of degrees of arc, the reference points on the surfaces of the larger rolls deviates farther from their original plane than do the reference points on the surfaces of the smaller rolls. In this situation, while the angle between the lines of tangency of the small rolls and between the lines of tengency of the large rolls is the same, the resulting deformation of the briquettes is more significant with the larger rolls since larger briquettes are formed. Furthermore, since the reference points deviate farther from their original plane, the briquette-forming cavities on the sides of the rolls away from the point of articulation are farther apart thereby producing a briquette of reduced and irregular density.
The briquetting press is greatly simplified by articulating only one briquette-forming roll. However, if the articulated roll articulates about a point on the longitudinal axis of its drive shaft, with large rolls the deformation of briquettes is even more significant than when both rolls are articulated. This is because the reference point on the surface of the single articulated roll deviates substantially from its original plane and, unlike a press where both rolls are articulated, the briquette-forming cavities in the surfaces of the rotating rolls are no longer in complementary relationship to each other since the reference point on the non-articulated rotating roll remains in the original plane.
Therefore, in order to design an industrial-sized briquetting press of simplified construction, it is very desirable to use a single articulating roll and reduce the deviation of the reference point on the surface of that roll from its original plane to an acceptable minimum. The present invention alleviates many of the difficulties encountered when using large briquetting rolls. By placing the point of articulation on a line which is parallel to and substantially midway between the axes of rotation of the drive shafts of the briquette-forming rolls and which is substantially tangent to both rolls and by articulating only one roll, roll deviation from the ideal and the concommitant briquette deformation is significantly reduced thus making possible the use of large rolls.
Prior art briquetting presses, besides being limited in size, are generally complicated in structure and usually enclosed in a housing making access to the press for repair or maintenance difficult. U.S. Pat. No. 3,134,156 is an example of the complicated design and all-encompassing housing.
Besides the necessity for repair and maintenance, it is frequently necessary to change the briquette-forming cavities in the peripheries of the rolls or to change the rolls themselves. Many of the prior art briquetting presses made it difficult to remove the rolls or change the peripheral cavities in the rolls.
Another difficulty encountered in prior art briquetting presses, especially in large presses utilizing significant pressure, is the movement of the briquetting rolls relative to each other during the briquetting process. In order to produce uniform briquettes in size, shape and density, it is necessary that the briquetting cavities in the periphery of the rolls be consistently in cooperative relationship. Any deviation of the rolls in a direction parallel to the longitudinal axes of the roll shafts or normal to the plane containing the shafts will cause the production of deformed, cracked, sheared or unusable briquettes.
Furthermore, prior art briquetting presses were deficient in their application of briquetting pressure in that the pressure was inconsistent, thereby producing briquettes of inconsistent density. Prior art briquetting presses providing inconsistent pressure and permitting periodic deviation of the briquetting rolls from their cooperating relationship produced a significant percentage of unacceptable briquettes.